Stabilized poly-alpha-olefin compositions



ited States 2,964,497 STABILIZED POLY-a-OLEFIN COMPOSITIONS Charles J. Kibler and Gordon C. Newland, Kingsport,

Tenn., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Mar. 24, 1958, Ser. No. 723,113 .12 Claims. c1. est-45.85

v This invention relates to the stabilization of poly-mol'e'fi'n compositions. A preferred embodiment of the invention relates to the stabilization of polyethylene compositions against deterioration resulting from exposure to sunlight or ultraviolet light.

Poly-a-ole'fins such as polyethylene, polypropylene and the like are subject to photooxidation when exposed to sunlight. This oxidation in poly-a-olefins is characterized in its earlier stages by the breaking of the polymer chain and the formation of carbonyl groups in the molecule with 'a resultant defete'riou's effect on the electri'cal properties or the polymer. As the oxidation continues, the poly-a-olefin cracks and loses tensile strength to the point of mechanical "failure. A number of socalled ultraviolet inhibitors '-are known which "inhibit the photo-degradation of many polymers, resins and polyesters. However, some of the mostefiective of these known ultraviolet inhibitors, such as 2,4-dihydroxy benzophenone, aretnot compatible with such poly-a-olefins as jpolyethyle'ne due to exudation from,thepolyethylene soon after being incorporated therein. Also, there are other common ultraviolet inhibitors, that are :compatible with polyethylene but -are .not. entirely satisfactory stabilizers for po'yethylene, typical of suchflstabilizers being phenyl salicylate. In addition, many effective stabilizers for halogen-containingpolymers such as polyvinyl chloride, gpolyvinylidene chloride, poly(2,3-dichloro-l,3-butadene) and the like are 'not'necessarily effective stabilizers for :poly-wolefins, as stabilizersinhalogen-containing poly- '-mers function essentially as halide scavengers while stabilizers in-poly-u-olefins do not serve this function.

, Similarly, certain stabilizersthat are imminently suitable as ultraviolet inhibitorsinsuch cellulosicesters as cellulose triacetate, cellulose acetate butyrate and the like are not particularly effective in'poly-a-olefins. Hence, it is highly unpredictableas to whethera given stabilizer or ultraviolet inhibitor will be both compatible with, and agood stabilizer for, poly-a-olefin compositions short of actually testing thematerial in polya-olefins.

It is an objectofthis invention'to-provide new poly-aolefin compositions of high stability.

It is a further 'object of this invention to provide novel polyethylene compositions containing additives .that'are compatible with, and effective stabilizers for, the

- polyethylene compositions.

-the description-and claims which follow.

The present invention comprises =polyi-cz-olefin wcompositions having incorporated therein a stabilizing amount of one" of the following' fl resorcylic acid derivatives:

O CHa 4-acetyl-B-resorcyli acid C O O H OCCHII 2-acetyl-5-resorcyllc acid C O O H 0C OH:

diacetyl-fl-resorcylic acid H OQ'E on .pol y- (fl-resorcylic acid) H poly- (t-acetyl-fl-resorcylic acid) The fi-resorcylic acid derivatives described herein can be used to stabilize a Wide variety of poly-ot-olefin compositions against deterioration resulting from exposure to ultraviolet light. Any of the common normally solid 'poly-a-olefins prepared from the normally gaseous amonoolefinic aliphatic hydrocarbons containing 2 to 10 carbons atoms can be stabilized in accordance with the invention. The present ,B-resorcylic acid derivatives are preferably used in polyethylene although such poly-aolefins as polypropylene, poly-4-methylpentene-1, poly-3- methylbutene-l, and the like are included in the present invention. Both the so-called, low density and high density poly-a-olefin compositions can be stabilized in accordance with the invention. With regard to polyethylene, tor example, low density polyethylene usually has a density of about 0.91 to 0.93 and can be prepared by several methods including the method disclosed by Fawcett et al. in US. Patent No. 2,153,553. High density polyethylene usually has a density of about 0.94 to 0.97. High density poly-a-olefins can be prepared by such methods as are disclosedin co-pending applications, Coover U.S. Serial No. 559,536 which was filed January 17, 1956 and Coover U.S. Serial No. 613,609 which was filed October 3, 1956. While the subject stabilizers are .moresusually used to stabilize themore common solid at least 0.1% are suitably used, with concentrations of 0.1% to 10% being more generally used, with concentrations of 0.5% to and often times 0.5% to 2.5% being preferably used, the concentrations of the stabilizer being based on the weight of the poly-a-olefin.

The stabilizers of the invention can be incorporated or blended into poly-a-olefins by any of the conventional methods used for blending such materials into plastics 0r resins. Typical of such methods that can be suitably L employed include milling on heated rolls, deposition from solvents and dry blending.

The fl-resorcylic acid derivatives described herein lend to poly-a-olefin' compositions improved stability, and more specifically, improved stability against deterioration resulting from exposure to outdoor weathering, sunlight or ultraviolet light. Polyethylene compositions'are sometimes protected against outdoor weathering with carbon black pigment or related opaque materials. However, such pigments limit the outdoor use of polyethylene compositions so protected to uses where color and trans parency are unimportant. The present ,B-resorcylic acid derivatives do not impart objectionable coloration to polya-olefin compositions and thus poly-a-olefin compositions stabilized therewith can be utilized for a wide diversity of outdoor uses.

Poly-a-olefin compositions stabilized in accordance with the invention can be cast, extruded or molded into sheets, rods, tubes and piping, filaments and other shaped articles. The compositions can also be used for coating paper, cloth, wire, metal foil, glass fiber fabrics, synthetic and natural textiles and other such substances. Poly- (fi-resorcylic acid) and poly-(4-acetyl-p-resorcylic acid) have particular utility in thin films or sheets 0.5 to 100 mils in thickness, for example, as these polymeric compounds tend to be more non-migratory in the poly-uolefin than monomeric stabilizers and thus confer stability to thin films or sheets for relatively long periods of exposure.

The invention is illustrated by the following examples of preferred embodiments thereof.

EXAMPLE 1 Into several portions of polyethylene having an average molecular weight of about 30,000 and a density of 0.945 was hot-roll compounded 1% by weight of the following compounds: 4-acetyl-[3-resorcylic acid, 2-acetylfl-resorcylic acid, diacetyl-fi-resorcylic acid, poly-([3- resorcylic acid) having an average molecular weight of 7 355, and poly-(4-acetyl-fl-resorcylic acid) having an average molecular weight of 280. The resulting compositions were thereafter compression-molded into sheets about A inch thick, ten samples 1 /2 by /2 inch were ti'ced out of the compression-molded sheets, bent into a U-shape and exposed to outdoor weathering at Kingsport, Tennessee. The stressed portion of each sample was mounted facing south. Ten additional samples containing no stabilizer were prepared and also subjected to the weathering test for comparative purposes. The exposure times in days required to start cracks in half As can be observed from the data in Table 1, the Subject B-resorcylic acid derivatives are effective stabilizers in polyethylene against deterioration resulting from exposure to sunlight, the stress cracking resistance of the polyethylene samples containing the fl-resorcylic acid derivatives being increased 26, 40, greater than 90, 26 and 29 days respectively over the polyethylene sample containing no stabilizer. All of the added stabilizers were compatible with the polyethylene sample and did not exude therefrom during the course of the weathering test.

EXAMPLE 2 Into polyethylene having an average molecular weight of about 27,600 and a density of 0.919 was hot-roll-compounded 1% by weight of poly-(4-acetyl-p-resorcylic acid) having an average molecular weight of about 280. The resulting composition was compression molded into a film 5 mils thick and cut into 2 /2 by /2 inch samples. Similar polyethylene samples containing no additive were also prepared. The thus prepared samples were exposed to artificial weathering in an Atlas Twin-Arc Weather- Ometer described in Analy. Chem., 25, 460 (1953) that was modified by the addition of 10 Westinghouse 20 watt fluorescent sun lamps. The exposed samples were tested for deterioration after 400 hours and after 800 hours of exposure to the artificial weathering by elongation measurements on an Instron Tensile Tester at a rate of stretch of per minute. The samples were conditioned 3 days at 73 C. at a relative humidity of 50% before testing. The results of the test are summarized EXAMPLE 3 Into several portions of polyethylene having an average molecular weight of about 30,000 and a density of 0.945 was hot-roll-compounded 1% by weight of diacetyl-p-resorcyclic acid and poly-(4-acetyl-j3-resorcyclic acid) having an average molecular weight of about 280, as well as 1% by weight of p-tertiary butylphenyl salicylate for comparative purposes. The resulting compositions were compression molded into films 5 mils thick and cut into 2 /2 by /2 inch samples. Similar polyethylene samples containing no additive were also prepared. The thus prepared samples were exposed to artificial weathering in an Atlas Twin-Arc Weather-Ometer described in Anal. Chem. 25, 460(1953) that was modified by the addition of 10 Westinghouse 20 watt fluorescent sun lamps. The exposed samples were tested for deterioration after 410 hours of exposure to the artificial weathering by elonga' tion measurements on an Instron Tensile Tester at a rate of stretch of 2,000% per minute. The samples were conditioned 3 days at 73 C. at a relative humidity of 50% before testing. The results of the test are summarized by the data set out in Table 3 below.

As can be observed from the data inTable 3, the subject B-resorcyclic acid derivatives are eifective ultraviolet inhibitors for thin films of polyethylene.

EXAMPLE 4 Into several portions of polypropylene having a melt index (A.S.T.M. D12 38-52T) of 0.08 and an ash content of 0.43% was extrusion-compounded 1% by weight of poly-(4-acetyl-B-resorcyclic acid) having an average molecular weight of about 280 as well as 1% by weight of Z-mercaptobenzimidazole for comparative purposes. 'The resulting compositions were extruded into a film 20 mils thick and then cut into 2 /2 by /2 inch samples. Similar polypropylene samples containing no additive were also prepared. The thus prepared samples were exposed to artificial weathering in an Atlas Twin-Air Weather- Ometer described in Anal. Chem., 25, 460 (1953) that was modified by the addition of Westinghouse 20 watt fluorescent sun lamps. Weathering damage to the exposed :samples was assessed as follows and summarized in Table 4.:

:(a) the fiexural strength of the samples was measured :after450d'1ours of exposure by the Tour-Marshall test for stiffness in fiexure (A.S.T.M. D747-43),

x('11.) .the percent of initial inherent viscosity of the poly- :propylene jleft after 95 hours of exposure as determined in tetra'lin solutions of 0.25 g. polypropylene per 100 cc. .of tetra'lin at 145 C., the polypropylene having an inlherent viscosity of 2.77. Inherent viscosity is defined as where r is the ratio of viscosity of solution to viscosity of solvent.

The compound, Z-mercaptobenzimidazole, used for comparative purposes was disclosed in U.S. Patent 2,727,879 as an effective light stabilizer for polyethylene.

The polymeric fl-resorcyclic acid derivatives of the present invention can be prepared by the methods disclosed in Examples 5 and 6 set out herein below. The polymers of B-resorcyclic acid used in the invention preferably are prepared as compositions having average molecular weights of about 250-500.

EXAMPLE 5 PREPARATION OF POLY- 4-ACETYL-B-RESORCYLIC ACID) Seventy-five grams of 4-acetyl- 8-resorcylic acid were thoroughly ground in a mortar with 1 /2 grams of zinc chloride. This mixture was placed in a 500 ml. Erlenmyer flask and heated in a metal bath maintained at 130- 135 C. The internal temperature of the resulting mixture gradually rose to 118-120 C. during 20 minutes, at which 7 point the mixture began to melt. About 5 minutes were required to melt the mass completely whence acetic acid vapors distilled off. The mixture was heated minutes longer at 120-126 C. Manual stirring was employed throughout the operation. The resulting mixture was then cooled to 50-60 (3., dissolved in 190 ml. acetone and the acetone solution filtered into 1500 ml. of vigorously stirred cold water which precipitated the product as an easily filterable powder. The resulting p0ly- (#Eaeety-l- 8-re1sorcyclic acid) had an average molecular weight of about 300.

A M PREPARATION OF Po'LY s-REsoR'cYmo ACID A solution of 10 g. of poly-(4-acetyl-B-resorcyclic acid), as prepared in Example 5, in a mixed solvent of 40 ml. of acetone, 20 ml. of water and"14 ml. of ammonium hydroxide (28%) was allowed to stand at 25- 30 C. for 1.5 hours to hydrolyze off the terminal acetyl groups. The resulting poly-(fl-resorcylic acid) was isolated by acidifying the solution with 16 ml. of 35% hydrochloric acid in 64 m1. of water. The resulting precipitated solid was filtered and washed with water to yield 3.5 g. of poly-(fi-resorcyclic acid).

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof it will be understood that variations and modifications can be eifected Within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A solid poly-a-olefin composition comprising a solid poly-a-olefin prepared from an a-monoolefinic aliphatic hydrocarbon having 2 to 3 carbon atoms containing 0.1% to 10% by weight based on said polya-olefin of a B-resorcylic acid derivative selected from the group consisting of 4-acetyl-fl-resorcylic acid, 2-acetylp-resorcylic acid, diacetyl-fi-resorcylic acid, poly-(B-resorcylic acid) and poly-(4-acetyl-[3-resorcylic acid), said poly-(,B-resorcylic acid) and said poly-(4-acetyl-fi-resorcylic acid) having an average molecular weight of about 250 to 500.

2. A solid polyethylene composition comprising solid polyethylene containing 0.1% to 10% by weight based on said polyethylene of a fi-resorcylic acid derivatve selected from the group consisting of 4-acetyl-B-resorcylic acid, Z-acetyl-B-resorcylic acid, diacetyl-B-resorcylic acid, poly-(fl-resorcylic acid) and poly-(4-acetyl-fi-resorcylic acid), said poly-(B-resorcylic acid) and said poly-(4- acetyl-fi-resorcylic acid) having an average molecular weight of about 250 to 500.

3. A solid polyethylene composition comprising solid polyethylene containing 0.5% to 5% by weight based on said polyethylene of 4-acetyl-{3-resorcylic acid.

4. A solid polyethylene composition comprising solid polyethylene containing 0.5% to 5% by weight based on said polyethylene of Z-acetyI-fi-resorcylic acid.

5. A solid polyethylene composition comprising solid polyethylene containing 0.5% to 5% by weight based on said polyethylene of diacetyl-jS-resorcylic acid.

6. A solid polyethylene composition comprising solid polyethylene containing 0.5% to 5% by weight based on said polyethylene of poly-(,B-resorcylic acid) having an average molecular weight of about 250 to 500.

7. A solid polyethylene composition comprising solid polyethylene containing 0.5% to 5% by weight based on said polyethylene of poly-(4-acetyl-j8-resorcylic acid) having an average molecular weight of about 250* to 500.

-8. A solid polypropylene composition comprising solid polypropylene containing 0.5% to 5% by weight based on said polypropylene of poly-(4-acetyl-fi-resorcylic acid) having an average molecular weight of about 250 to 500.

9. A solid poly-u-olefin composition in a film 0.5 to mils in thickness comprising a solid poly-u-olefin prepared from an a-monoolefinic aliphatic hydrocarbon having 2 to 3 carbon atoms containing 0.5% to 5% by weight based on said pOly-cc-Olefin of poly-(fi-resorcylic acid) having an average molecular weight of 250 to 500.

10. A composition as described in claim 9 wherein the poly-a-olefin is polyethylene.

11. A solid poly-a-olefin composition in a film .0.5 to 100 mils in thickness comprising a solid poly-a-olefin prepared from an a-monoolefinic aliphatic, hydrocarbon 7 having 2 to 3 carbon atoms containing 0.5% to 5% by weight based on said poly-a-olefin of po1y-(4-ac'ety1-firesorcylic acid) having'an'average molecular weight of 250 to 500.

12. A composition as described in claim 11 wherein 5 2,837,490

the poly-a-olefin is polyethylene- 7 References fiited inthe'fiic of this patent UNITED STATES. PATENTS 2,734,000 Pessel Feb. 7, 1956 Hecker- June 3, 1958 2,843,517

Friedlander et a1. July 15, 1958, 

1. A SOLID POLY-A-OLEFIN COMPOSITION COMPRISING A SOLID POLY-A-OLEFIN PREPARED FROM AN A-MONOOLEFINIC ALIPHATIC HYDROCARBON HAVING 2 TO 3 CARBON ATOMS CONTAINING 0.1% TO 10% BY WEIGHT BASED ON SAID POLYA-OLEFIN OF A B-RESORCYLIC ACID DERIVATIVE SELECTED FROM THE GROUP CONSISTING OF 4-ACETYL-B-RESORCYLIC ACID, 2-ACETYLB-RESORCYLIC ACID, DIACETYL-B-RESORCYLIC ACID, POLY-(B-RESORCYLIC ACID) AND POLY-(4-ACETYL-B-RESORCYLIC ACID), SAID POLY-(B-RESORCYLIC ACID) AND SAID POLY-(4-ACETYL-B-RESORCYLIC ACID) HAVING AN AVERAGE MOLECULAR WEIGHT OF ABOUT 250 TO
 500. 